1. Field
One or more example embodiments relate to semiconductor memory devices, for example, static random access memories (SRAMs) including carbon nanotube (CNT) films.
2. Description of the Related Art
Related art silicon (Si)-based semiconductor devices are relatively highly integrated, have relatively high performance, and are relatively inexpensive. Based on these advantages, processes of miniaturizing Si-based semiconductor devices have been continuously developed. However, about 5 to 10 years from now, the development of such miniaturization processes will likely slow and/or stop due to property limitations of Si and process difficulties.
As an alternative, research into electronic devices using carbon nanotubes (CNTs) is being performed. A diameter of a CNT may be as small as several nanometers (nm=10−9m). Thus, CNTs may be used to form micro channels that cannot be formed using Si-based miniaturization processes. Also, CNTs have excellent physical characteristics due to their structural characteristics such as charge mobility, current density, thermal conductivity, mechanical strength, etc. As a result, limitations in development of miniaturization processes of Si-based semiconductor devices may be overcome by using CNTs.
However, applying CNTs practically in electronic devices is somewhat difficult because CNTs have reliability problems. In addition, arranging CNTs in a given, desired or predetermined location is relatively difficult. To manufacture CNT electronic devices, a single-walled semiconducting CNT having a diameter of nanometers is needed to utilize the sufficient or excellent unique characteristics of CNTs. However, controlling changes in characteristics by changing a tube diameter is relatively difficult, and thus, CNTs are not suitable for practical use.
Recently, research into a CNT film used as an electronic device has been performed. For the CNT film, charge mobility is relatively low (e.g., about 10˜200 cm2/Vs, inclusive) compared to a single-walled CNT, but characteristic stability is relatively high and the manufacturing process is relatively simple.